The application of fundamental crystallization theory should lead to an improved understanding of the processes involved in the genesis of kidney stones and a more rational approach to the design and evaluation of therapy. Combining an intuitive approach with crystallization principles one would ask the following questions: 1) What starts crystallization in urine? - Nucleation; 2) How much can precipitate? - Supersaturation Level; 3) How fast can the precipitate form? - Crystallization Rate; 4) What form does the precipitate have? - Habit, Aggregation; 5) What accounts for retention of the precipitates in the kidney? - Size, Aggregation, Adherence to cell membranes,...? We have developed new techniques utilizing C14-oxalate and Calcium 45 to quantitate the following crystallization parameters of urinary calcium oxalate: 1) Supersaturation Levels; 2) Crystallization Rates; 3) Metastable Limits (Spontaneous Nucleation; 4) Heterogeneous Nuclei; 5) Binding - Adherence of Crystals to Tubular Cells. These techniques are being applied to: 1) elucidation of the molecular mechanisms regulating the above parameters of urinary calcium oxalate, and 2) evaluation and monitoring of the efficacy of antistone therapy on patient urines.